MyoD is a myogenic master transcription factor that plays an essential role in muscle satellite cell (muscle stem cell) differentiation. To further investigate the function of MyoD in satellite cells, we examined the transplantation of satellite cell-derived myoblasts lacking the MyoD gene into regenerating skeletal muscle. After injection into injured muscle, MyoD ؊/؊ myoblasts engrafted with significantly higher efficiency compared with wild-type myoblasts. In addition, MyoD ؊/؊ myoblast-derived satellite cells were detected underneath the basal lamina of muscle fibers, indicating the self-renewal property of MyoD ؊/؊ myoblasts. To gain insights into MyoD gene deficiency in muscle stem cells, we investigated the pathways regulated by MyoD by GeneChip microarray analysis of gene expression in wild-type and MyoD ؊/؊ myoblasts. MyoD deficiency led to down-regulation of many muscle-specific genes and up-regulation of some stem cell markers. Importantly, in MyoD ؊/؊ myoblasts, many antiapoptotic genes were up-regulated, whereas genes known to execute apoptosis were downregulated. Consistent with these gene expression profiles, MyoD ؊/؊ myoblasts were revealed to possess remarkable resistance to apoptosis and increased survival compared with wild-type myoblasts. Forced expression of MyoD or the proapoptotic protein Puma increased cell death in MyoD ؊/؊ myoblasts. Therefore, MyoD ؊/؊ myoblasts may preserve stem cell characteristics, including their resistance to apoptosis, expression of stem cell markers, and efficient engraftment and contribution to satellite cells after transplantation. Furthermore, our data offer evidence for improved therapeutic stem cell transplantation for muscular dystrophy, in which suppression of MyoD in myogenic progenitors would be beneficial to therapy by providing a selective advantage for the expansion of stem cells.apoptosis ͉ cell therapy ͉ microarrays ͉ muscular dystrophy ͉ satellite cell

Natural killer (NK) cell phenotype is partially mediated through binding of killer immunoglobulin-like receptors (KIR) with HLA class I ligands. The KIR gene family is highly polymorphic and not well captured by standard GWAS approaches. Here we tested the hypothesis that variations in KIR gene content combined with HLA class I ligand status is associated with keratinocyte skin cancers using a population-based study of basal cell carcinoma (BCC) and squamous cell carcinomas (SCC). We conduced an interaction analysis of KIR gene content variation and HLA-B (Bw4 vs Bw6) and HLA-C (C1 vs C2). KIR centromeric B haplotype was associated with significant risk of multiple BCC tumors (OR=2.39, 95% CI: 1.10–5.21), and there was a significant interaction between HLA-C and the activating gene KIR2DS3 for BCC (pinteraction = 0.005). Furthermore, there was significant interaction between HLA-B and telomeric KIR B haplotype (containing the activating genes KIR3DS1 and KIR2DS1) as well as HLA-B and the activating KIR gene 2DS5 (pinteraction 0.001 and 0.012, respectively). Similar but greatly attenuated associations were observed for SCC. Moreover, previous in vitro models demonstrated that p53 is required for upregulation of NK ligands, and accordingly, we observed there was a strong association between the KIR B haplotype and p53 alteration in BCC tumors, with a higher likelihood that KIR B carriers harbor abnormal p53 (p<0.004). Taken together, our data suggest functional interactions between KIR and HLA modify risks of BCC and SCC, and that KIR encoded by the B genes provide selective pressure for altered p53 in BCC tumors.

A single nucleotide polymorphism (SNP) 35 kb upstream of the HLA-C gene is associated with HLA-C expression, and the high expressing genotype (CC) has been associated with HIV-I control. HLA-C is unique among the classical MHC class I molecules for its role in the control of viral infections and recognition of abnormal or missing self. This immunosurveillance is central to the pathogenesis of non-melanoma skin cancer (NMSC), and of squamous cell carcinoma (SCC) in particular. While sun exposure is a major risk factor for these cancers, cutaneous infections with genus β-HPV have been implicated in the development of SCC. We hypothesized that the high expression HLA-C genotype is associated with β-HPV infections. Therefore, we investigated the association between β-HPV serology and the −35 kb SNP (rs9264942) in a population-based case-control study of 510 SCC cases and 608 controls. Among controls, the high expression −35 kb SNP genotype (CC) reduced the likelihood of positive serology for multiple (≥2) β-HPV infections (OR = 0.49, 95% CI: 0.25–0.97), and β-HPV species 2 infection (OR = 0.43, 95% CI: 0.23–0.79). However, no association with β-HPV status was observed among SCC cases. Our findings suggest that underlying immunogenotype plays an important role in differential control of β-HPV in SCC cases and controls.